It is known to obtain penicillamine by reaction of isobutyraldehyde with sulfur and ammonia and converting the thus obtained thiazoline-.DELTA..sup.3 by reaction with hydrogen cyanide to the corresponding thiazolidine-4-carbonitrile. The nitrile is then hydrolyzed by reaction with mineral acids. It is thus obtained, first, thiazolidine-4-acid amide and then thiazolidine-4-carboxylic acid and the ammonium salt. The ammonium salt is separated and the carboxylic acid is hydrolytically decomposed and thus converted into the penicillamine hydrochloride.
The present process is an improvement over the process of the above second noted U.S. application where the hydrolysis was carried out in two stages. In the first stage the reaction was effected at low temperature. In the second stage of the hydrolysis a higher temperature was then employed.